Lock washers are commonly used in many different fields. As a consequence, there are large varieties of lock washer configurations that have evolved over the years for use in specific environments. Many have detriments of one sort or another associated with their use.
For example, it is not unusual to provide lock washers that include a sharp edge or point displaced from the body of the washer so as to dig in or gouge one or both of the nut that is being locked and the surface to which the nut is applied. While these types of lock washers work well for their intended purpose in many environments, they are not satisfactory where corrosion presents a problem. More particularly, where such lock washers are used after a protective coating has been applied to one or the other of the components to be joined, the gouging action provided by the sharp edge will always penetrate the coating if a good locked joint is to be obtained. As a result, the protective coating is no longer continuous and moisture or other corrosive substances may penetrate the joint with corrosion resulting.
Other lock washers include lock tabs which are displaced in the plane of the body of the washer and which have flat free edges which are adapted to abut a flat of the nut to be locked. See, for example, U.S. Pat. No. 1,349,404 issued Aug. 10, 1920 to Blake. In this construction, a plurality of lock tabs greater in number than the number of flats on the nut to be locked is provided and all project away from the plane of the washer to be located about the periphery of the nut. While these types of lock washers work well in terms of providing the desired locking function, it is difficult to loosen the nut, and reuse of the lock washer may be a problem.
Typically, lock washers are made of a resilient metal and each of the lock tabs requires a force of 8-10 lbs. to depress the same back into the plane of the base of the washer. It is necessary to displace each tab back into the plane of the base of the washer to move it out of interfering relation with the flats of the nut if the nut is to be loosened.
When a number of the tabs are present as in Blake and other constructions, the total force involved may be 65-80 lbs. While such a force may be applied axially through the use of a socket wrench, where it is necessary to loosen the nut with a box end or open end wrench, the average user of such a tool is incapable of applying such a force over the lever arm represented by the length of the wrench, making removal difficult, if not impossible.
Furthermore, such constructions are extremely difficult to loosen with an open end wrench even if the force of the locked tabs can be overcome. Specifically, an open end wrench, by reason of its open ended geometry, will typically be incapable of depressing all of the lock tabs which in turn means that one or more lock tabs will spring into locking position in abutment with the flat of the nut, preventing its rotation.
If, in such a situation, rotation of the nut is forced, then the lock washer will be permanently distorted and cannot be reused.
French patent document 1,394,517 issued Feb. 22, 1965 to Bruhwiler, et al., provides a means of at least overcoming potential corrosion problems through the use of a locating tab on the body of the lock washer which may be received in a notch or recess in the surface to which the lock washer is applied to prevent the lock washer from rotating. However, Bruhwiler continues to employ a large number of lock tabs that require substantial force to displace into the plane of the washer body and which prevent ready loosening of the nut with a tool such as an open end wrench. Furthermore, the pointed lock tabs of Bruhwiler may hinder loosening of the nut in that they may have a tendency to dig into the sides of the loosening tool and hinder its rotation. When such occurs, to the extent the rotation is forced, then the lock tabs are permanently deformed and the Bruhwiler lock washer cannot be reused.
U.S. Pat. No. 5,562,378, which issued Oct. 8, 1996 to Blechschmidt, discloses a lock washer having lock tabs which may be bent up, out of plane, to a position adjacent a flat of the nut. While this structure has been found to be advantageous in a number of ways, there is a trade off required in the strength (i.e., thickness) of the washer body relative to the lock tabs. Specifically, when the washer is relatively thick, the bending of the lock tabs may require an unacceptably large force. By contrast, when the washer is relatively thin, while the lock tabs may bend more easily, engagement of the lock tabs by a socket may be more difficult. Moreover, a thin washer will not only be weaker but the washer body may also be so thin around its center opening as to undesirably fall into the pitch of the bolt thread.
An improvement upon U.S. Pat. No. 5,562,378 has been to provide a thin washer and to weld a ring-like portion onto the top of the washer body. While this has assisted in preventing the center of the washer body from falling into the pitch of the bolt thread while leaving more easily bent lock tabs, engagement of the lock tabs can still be difficult, and the handling of pieces, and related cost and time required for production of such lock washers, can be significantly higher than that associated with the lock washer of U.S. Pat. No. 5,562,378.
The present invention is directed to overcoming one or more of the above problems.